desktop: Remove "rust" keyword from Linux metadata

Keywords are used for searching and Ruffle shouldn't be a result when
searching for "rust", as users usually expect e.g. tools and IDEs
related to programming in Rust.

desktop/packages/linux/rs.ruffle.Ruffle.desktop.in

@@ -7,4 +7,4 @@ Icon=rs.ruffle.Ruffle
 Exec=ruffle %u
 MimeType=application/x-shockwave-flash;application/vnd.adobe.flash.movie
 Categories=AudioVideo;Player;Graphics;Viewer;VectorGraphics;Game
-Keywords=flash;swf;player;emulator;rust
+Keywords=flash;swf;player;emulator

desktop/packages/linux/rs.ruffle.Ruffle.metainfo.xml.in

@@ -43,7 +43,6 @@
         <keyword>swf</keyword>
         <keyword>player</keyword>
         <keyword>emulator</keyword>
-        <keyword>rust</keyword>
     </keywords>
     <url type="homepage">https://ruffle.rs</url>
     <url type="bugtracker">https://github.com/ruffle-rs/ruffle/issues</url>